LibRequests+LibWeb: Release response pipes for canceled fetches and parked navigations by sideshowbarker · Pull Request #11041 · LadybirdBrowser/ladybird

sideshowbarker · 2026-08-07T17:27:24Z

8cf2654 now closes a completed response stream once all reported bytes have been delivered — so the ordinary-completion leak this branch originally fixed is already handled. What remains here is the regression test that fix shipped without, plus two leak paths 8cf2654 didn’t reach:

Test that completed requests release their pipes
Release response pipes when fetches are canceled
Tear down a navigation parked for content sniffing

Details are in the the individual commit messages. Fixes #11142.

coderabbitai · 2026-08-30T07:28:22Z

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Actionable comments posted: 2

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Inline comments:
In
`@Tests/LibWeb/Text/input/Fetch/response-pipes-released-after-cancellation.html`:
- Line 24: Update the fetch cancellation test around pending and the polling
logic to fail if the pre-abort response-pipe count remains zero, ensuring a
response pipe was actually opened before cancellation is asserted. Replace the
unconditional catch on fetch with handling that ignores only the expected abort
rejection while propagating setup or network failures, and apply the same guard
to the related lines.
- Line 46: Update the test cleanup flow around the fixture-unblock fetch to
await its completion before invoking done(), while preserving the existing
rejection handling; ensure done() is called only after the request settles so
the fixture is reliably released.

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Tests/LibWeb/Text/expected/Fetch/response-pipes-released-after-cancellation.txt
Tests/LibWeb/Text/input/Fetch/response-pipes-released-after-cancellation.html

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Actionable comments posted: 1

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Inline comments:
In
`@Tests/LibWeb/Text/input/Fetch/response-pipes-released-after-parked-navigation.html`:
- Around line 26-29: Update the polling logic in the test to require observing a
nonzero internals.openResponsePipeCount() before removing the iframe; fail the
test if that parked-state condition is not reached, or replace the polling with
a deterministic signal from the parked navigation. Do not rely on the fixed
timeout alone.

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Libraries/LibWeb/HTML/NavigationParamsDescriptor.cpp
Tests/LibWeb/Text/expected/Fetch/response-pipes-released-after-parked-navigation.txt
Tests/LibWeb/Text/input/Fetch/response-pipes-released-after-parked-navigation.html

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Every HTTP request receives its response body through a RequestServer pipe that pins an open fd in the process that issued the fetch. A page fetching in a tight loop can starve that process of descriptors if completed requests keep their pipes until GC runs — since the scarce resource is descriptors, while GC pressure is measured in heap bytes. Requests::Request closes a completed stream once all reported bytes have been delivered, so a descriptor goes back promptly. Nothing covered that. This adds a test that fetches in a loop and then reads how many response pipes are still open — along with the ReadStream::live_count() counter, and the openResponsePipeCount() Internals hook that reads it. Drop the close, and the test reports ten open pipes for eight fetches.

Problem: Aborting or terminating a fetch left its response pipe open for the lifetime of the process. A page that starts and cancels requests in a loop (an EventSource closed and reopened, a fetch or XHR aborted while the response is still hanging) leaked one file descriptor per cycle — until it ran out of them. Cause: abort() and terminate() only set the controller state. The one path that releases the request, stop_request(), is reached only from stop_fetch() — which returns early once the state is already “aborted” or “terminated”. So the two entry points that mark a fetch as canceled were the two that never told the network layer — and RequestServer holds a request alive until it either finishes or is stopped. Fix: Release the request from abort() and terminate() too — through a helper that stop_request() now shares. One caller relied on terminate() leaving the request alone. When a navigation response becomes a download, the request is handed to the UI process and the fetch is then terminated. That path now drops its handle to the request before terminating — so a download already under way isn’t stopped. RequestServer reports the transfer back to the WebContent process — and that’s what closes the reader end of the pipe. An abort can also land in between issuing the network request and the controller taking ownership of it. The releases above have all already run by then — and the request would sit on a controller that nothing will ever stop again. So, a controller that’s no longer ongoing now stops a request on the spot — instead of taking ownership of it.

Problem: Removing an iframe whose response headers had arrived but whose body hadn’t arrived left the network request open for the lifetime of the process. A page that adds and removes such iframes in a loop leaked one file descriptor per iframe. Cause: If a navigation has a response but not yet enough bytes to sniff its content type, it gets parked in wait_for_sniff_bytes. It has no document at that point — so, Document::abort() has no fetch controller to stop, and the only code that releases the request is the arrival callback. That callback does handle a destroyed navigable — but it runs only once bytes arrive. So, a server that sends headers and then stops leaves nothing at all around to release the request. Fix: Register a teardown on the navigable before parking — and run it if the navigable is destroyed first. The teardown calls the same helper the arrival callback already uses — and destroying a navigable is where the rest of its in-flight navigation state is released. The teardown releases the request through the navigation params’ fetch controller. Navigation params rebuilt from a descriptor carried none — even though the adopted response still holds the live RequestServer request — and every navigation is rebuilt that way on its way into population. So, hand those params a controller that owns the adopted request — the way create_navigation_params_by_fetching() builds its params. Every bail path that stops a fetch through the params gets a working stop from this — not just the new teardown. A navigation superseded before its populate task runs leaked the same way — for the same reason: That guard returned without releasing anything. It now releases the response as the guard above it does.